Great park in Groton.
Plenty to do nearby within the network of parks in the area. Solid hikes and legit beach at Boulder Beach State Park.
The new, nearby nature center is great, super clean, with interesting exhibits to keep science/nature minded kiddos busy.
You have to check in at Stillwater park and can't buy wood or ice onsite (also at Stillwater).
Note, don't plan on having cell service (welcome to VT). No one in our party did, across three major carriers (Verizon, ATT, TMobile)